Victims of cancer are often treated using chemotherapy and/or radiation therapy. Chemotherapy is the treatment of cancer by using drugs that destroy cancer cells. Radiation therapy is the use of a type of energy, called ionizing radiation, to destroy cancer cells.
Brachytherapy is one type of radiation therapy used to treat cancer. Brachytherapy involves placing a small amount of radioactive material inside the body, near the cancer cells or tumor. Unlike external radiation treatment such as electron beam irradiation, brachytherapy enables a doctor to use a higher total dose of radiation to treat a small area in a shorter amount of time. Brachytherapy may be temporary or permanent. In temporary brachytherapy, radioactive material is placed near the cancer cells or tumor for a fixed period of time, and then withdrawn. In permanent brachytherapy, radioactive material in the form of “seeds” is permanently placed near the cancer cells or tumor. Although the seeds remain in the body permanently, the radiation levels of the seeds drop off over time as radioactivity of the seeds decays.
In High-Dose Rate (HDR) brachytherapy, a specific high dose of radiation is delivered to the affected area through the delivery device for a short period of time controlled by a computer. This process may be repeated several times over the course of a single day. In Low-Dose Rate (LDR) brachytherapy, a lower dose of radiation is continuously delivered to the affected area through the delivery device over the course of hours or days.
LDR Brachytherapy has been used in the treatment of numerous types of cancer, including breast, lung, head and neck, and prostate. Cancer patients in need of brachytherapy require certain treatment regimens, i.e., a discrete number of radiological seeds arranged in a defined configuration. For example, different dosing levels or numbers of seeds may be required depending on various factors, e.g., the size of the patient, the nature of the tissue in which the seeds are to be implanted, and the type of cancer being treated.
For example, prostate cancer or other cancers may be treated using Palladium-103 or Iodine-125 seeds. Depending on the prostate size and aggressiveness of the cancer, a health care provider can determine the number and positioning of the radioactive seeds needed to deliver a sufficient amount of radiation to kill the cancerous cells.
To apply seeds to the cancer cells or tumor, a hollow tube delivery device such as a needle, catheter, or applicator may first be inserted into the affected area. Seeds are then placed in the delivery device and either pushed down the device into the proper location, or the delivery device is itself drawn out leaving the seeds seated in the proper location. Alternatively, the seeds may first be placed into the delivery device prior to the insertion of the delivery device into the body. For example, in certain brachytherapy delivery systems, the requisite number of radioactive seeds are loaded into brachytherapy needles and then inserted into the prostate. Once the tip of the needle has been placed in its proper position, the needle is withdrawn, leaving a pattern of seeds and/or spacers in place. X-rays, ultrasound, CT, or MRI scans may be among the tools used to ensure that the seeds in the strands are properly placed.
Proper seed placement and seed retention at the implantation site influence the success or failure of a brachytherapy procedure. Certain seed implantation devices and methods often provide variable seed spacing and dosimetric patterns during and after implantation. Loose seeds, especially those that are extra-capsular (located outside the capsule of the prostate), tend to migrate and/or rotate within the patient, and as a result, may not provide radiation where needed and may sometimes cause damage to other radiation-sensitive areas of the body.
Seeds can be linked together by a connector or connective material to form a series of linked seeds or a strand of seeds. The seeds in a particular series of linked seeds or a strand may be spaced apart by a predetermined interval to create a desired dosing level. By varying the spacing of seeds and the lengths of series of linked seed or strands, linked seeds or strands can be formed with different desired dosing levels. However, even linked seeds or strands of seeds can migrate and/or rotate within the body.
Upon implantation, movement or migration of brachytherapy seeds occurs most frequently along the needle track cut by the needle during insertion. The desire to have the needle (and subsequently the seed) in the exact desired position prior to seed deployment can require several attempts to reposition the needle with new needle tracks resulting from each attempt. These repeat attempts may also contribute to gland edema and the resulting adverse effects on dosimetry.
It is theorized that seeds can move in the needle track since the track itself has a larger cross section than the seed outside diameter. For example, brachytherapy seeds are commonly deployed using an 18 G needle, with an inner diameter of 0.040″ and an outer diameter of 0.048″. The tissue is cut to the approximate size of the needle or just slightly smaller resulting in a cross section “cut” of about 0.040″ to 0.048″. This cut or needle track is larger than the common brachytherapy seed having an outer diameter of 0.032″ and an assembled SourceLink® train having an outer diameter of 0.038″. Accordingly, this larger track size appears to allow a seed some degree of movement along the cut track
The systems, assemblies, and/or devices disclosed herein aid in fixing an implanted seed in place and preventing migration and/or rotation of implanted seeds. Further, the delivery device disclosed herein reduces the degree of trauma to the patient and helps prevent migration along the needle track.